Soundstage disappeared!?

Not sure what happened but this weekend while listening to my system, during a song I noticed the bass went neutral & the instruments disappeared into the back of the room? Up until that time, when I played music it was if I was in the room, concert hall, etc. with the musicians. Not anymore.

The 411 on my system is:

Pioneer PD-F606 CD Player

Pioneer SG9800 EQ

Denon DRA-335R tuner

Audience Ohno Interconnects

16/2 stranded copper speaker wire

8 speakers (8 ohm) Pioneer, Kenwood & Technics

This weekend I'll be able to swap out components to identify the source of the problem but wanted to get you guys opinions on what could be the problem. I'm leaning towards the tuner but will admit I'm electrically incompetent. If it's the tuner, what happened? If it's the equalizer, what happened? Did the speakers crossover? I hope you guys have some way to send me that I haven't already thought of.

Thanks in advance

Did you by any chance turn off your system for the first time in a while, and then try again?

vista1868 writes:
 while listening to my system, during a song I noticed the bass went neutral & the instruments disappeared into the back of the room...
8 speakers (8 ohm) Pioneer, Kenwood & Technics

Did you really connect 8 speakers to just the one reciever? If so then you could easily have a low ohm situation that tripped a protective circuit. But then I don't understand "the back of the room." Are a couple speakers connected to something else?
Disconnect everything. Start over. Set it up for 2 speakers. 
@Eric  Yes I did. The clarity, etc. is there but the sound of being in the concert hall now sounds like I'm listening in a bar with bad acoustics. 

@Miller carbon yes 8, because they were there from my A/V system & I figured hell give it a go & the system has been doing quite fine for almost a year. I can't turn it to loud without the wife complaining. If it's a protective circuit, where would I begin looking for it?
Is it possible you have one speaker connected out-of-phase? try reversing the polarity of just one speaker by swapping red and black wires.
When going from a multichannel receiver to a stereo receiver, driving the same 8 speakers, things are definitely going to sound different. The DRA 355R receiver is 40 watts, and not rated to play below 4 ohms. If the prior receiver was an avr unit, the speakers were being driven by separate amplifiers within the chassis. I am not surprised by what you are hearing. And, depending on whether you wired the speakers in series or parallel, I am surprised you have / have not tripped the protection circuits of the Denon receiver, as mentioned by millercarbon above.
This is the part that gets me:
while listening to my system, during a song I noticed the bass went neutral & the instruments disappeared into the back of the room

Is this correct? This wasn’t something that happened who knows when and then you noticed, this is something that actually happened WHILE you were listening???

Because what I said about the protective circuit is based on this one statement. That this is something that happened during a song. Everyone else’s ideas would be things that happened whenever, who knows, and then you just happened to notice it.

If its something that happened suddenly and during play then it has to be either a protective circuit that tripped or your receiver has a problem. Which by now if its been off and on again then it won’t be a circuit and Houston, we have a problem.

To check this out disconnect all but one pair of speakers. See how it sounds with just one pair. If your receiver has multiple speaker terminals then check that one pair with each set of terminals. Then disconnect that pair and do the same with the next. And so on, until you have confirmed all speakers work properly when connected one at a time. Then if they all work individually connect additional pairs of speakers one pair at a time checking each time to see how they sound.
Hey Vista, 

If you turned everything off overnight for the first time in a while, this makes sense. Some equipment takes time to warm up. Some Class D amps especially take 72-100 hours to sound their best.

If that's what you did, I suggest you leave everything alone for a couple of days. :) 



Thank you everyone for helping.

I can't seem to find a service manual for this unit to be able to troubleshoot so if I take this to someone to check it out, what parameters do they have to go by? Maddening I tell you. I thought about buying a new one but that is a risk in of itself because I can't see, hear or even get a response from some sellers ( afraid to answer the important questions by past results). 

I have a Nakamichi at work that I'll bring home Friday to see if the sound comes back.

Anybody out here a Denon technical guru? Probably not but worth a shot